In a recent study of 48 subjects, the applicant found that the number of propionibacteria on the forehead varied from more than 100,000 per cm2 in 17 persons to fewer than 1,000 on 7 subjects. Repeat culture after several months showed a consistent difference between 8 subjects with a rich initial population and 8 with a poor population of propionibacteria. He has proposed that a rich population of propionibacteria is an expression of a specific microbial ecosystem designated "eupropic". Subjects with few propionibacteria are designated "oligopropic". They do not represent a single ecosystem as there is considerable diversity in their microbial populations. This study is designed to determine whether the full spectrum of different microbial populations found in the above study also occurs on the skin of the face of persons with acne. We will characterize the range of flora that occurs in association with acne. This will be compared with the flora of matched controls having little or no acne. Serial studies will be made of certain individuals who undergo marked changes in the extent of acne. Characterization of flora will be quantitative aerobically and anaerobically and will discriminate between Propionibacterium granulosum and P. acnes types 1 and 2 as well as staphylococci and micrococci by the Baird-Parker methods and also by other characteristics that might be correlated with acne.